Sealing ring for a piston pump

ABSTRACT

A sealing ring is configured to dynamically seal a pistol in a piston pump. The piston is guided in a piston housing or in a guide ring. The sealing ring is arranged on an outer circumference of the piston. The outer circumference of the piston forms a running surface. The sealing ring has an outer circumferential surface with at least one circumferential groove. The sealing ring also has an inner circumferential surface with at least one circumferential sealing When the sealing ring is in an installed state, limbs of the at least one sealing lip each form a defined angle with the running surface. The defined angles are formed, starting from an initial angle, by deforming the sealing ring during installation. The sealing ring is twisted about a center of its profile during the installation.

PRIOR ART

The invention relates to a sealing ring for a piston pump according tothe generic type of independent patent claim 1 and to a piston pumpaccording to the generic type of independent patent claim 7.

DE 101 16 658 A1 describes, for example, a piston pump with a sealingring which is provided for the dynamic sealing of a piston of the pistonpump, said piston being guided in a piston housing, wherein the sealingring is to be arranged on an outer circumference of the piston, saidouter circumference forming a running surface. The sealing ringcomprises an annular basic body which has a substantially quadrangularcross section, and four encircling sealing lips which are formed at thecorners of the basic body and between which encircling grooves areformed.

DE 10 2004 010 498 A1 discloses a sealing ring which seals a piston of apiston pump and is composed of an elastomeric material. The sealing ringcomprises an annular basic body which has a substantially quadrangularcross section, and four sealing lips which are formed at the corners ofthe basic body and have grooves arranged in between. In order to improvethe durability characteristics, the sealing ring has a coating.

DISCLOSURE OF THE INVENTION

By contrast, the sealing ring according to the invention with thefeatures of independent patent claim 1 has the advantage that, startingfrom initial angles, the defined angles are achieved by deformation ofthe sealing ring during installation. This advantageously results in asealing ring which has an increased sealing effect and a longer servicelife by the sealing ring taking up its functionally relevant shape onlyin the installed state. A sealing ring is advantageously produced, saidsealing ring being able to be fitted in an undirected manner or nothaving to be aligned during fitting, thus permitting simple andcost-effective fitting of the sealing ring. This also means that aseparate identification process can be omitted. The risk of erroneousfitting, in which a massive leakage can subsequently occur and whichcannot be detected during operation of the piston pump, and a subsequentfailure of a complete unit can therefore be reliably avoided. Inparticular, the configuration of the construction space in the pistonhousing or guide ring can be designed in such a manner that the sealingring is fixable in an asymmetric position by the deformation of itsprofile, thus making it possible to achieve the function of anasymmetric sealing ring. In comparison to the production of anasymmetric sealing ring, this also results in lower tool costs, sincethe production of symmetrical parts is more cost-effective. In anadvantageous manner, the sealing ring comprises a groove in the outercross section or on the outer circumferential surface thereof in orderto support the pressing on of the sealing lip at higher pressures.

Advantageous improvements to the sealing ring indicated in independentpatent claim 1 are possible by means of the measures and developmentscited in the dependent claims.

In a refinement of the invention, the sealing ring undergoes twistingabout a center point of its profile during fitting. In this case, thesealing ring advantageously takes up its functionally relevant shapeonly in the installed state. The distortion of the profile of thesealing ring is preferably between 19° and 22°.

In a refinement of the invention, the sealing ring has two encirclinggrooves on the inner circumferential surface, said grooves forming twolips, between which the sealing lip is formed. It is particularlyadvantageous that the sealing lip protrudes over the lips in the radialdirection. The refinement makes it possible for the lips toadvantageously be kept away from the adjacent components of the pistonpump even at high pressures, i.e. neither touch the running surface norare at risk of gap extrusion.

In addition, the structure of the piston pump can remain unchanged,since the existing construction space in the piston pump easily permitsa change in the geometry of the sealing ring in the radial direction.

The sealing lip preferably has a radius which is between 0.1 and 0.4 mm.This advantageously results in a simple and cost-effective production ofthe sealing ring.

A substantial advantage of the piston pump according to the inventionconsists in that the sealing ring is arranged via at least three contactsurfaces in a groove running between two components of the piston pump.After the piston pump is fitted and the sealing ring is installed, thisadvantageously results in a secure position of the sealing ring withinthe groove. By means of the positional stability of the sealing ring,the desired dynamic sealing function is permanently maintained duringthe operation of the piston pump and, during the course of theoperation, the sealing ring withstands the existing pressure in thepiston pump.

In a refinement of the piston pump according to the invention, a firstlimb of the sealing ring is acted upon axially with a higher pressureand a second limb of the sealing ring is acted upon axially with a lowerpressure. In an advantageous manner, the sealing ring is securelymounted in the groove, and the hydraulic pressure can now only actslightly on the sealing ring, and therefore the sealing ring accordingto the invention can reliably carry out its sealing function. Thisadvantageously increases the service life of the sealing ring accordingto the invention, and therefore the maintenance interval can belengthened and the downtimes of the piston pump due to defective sealingrings minimized.

In a further refinement of the piston pump according to the invention,the defined angle between the first limb and a running surface of thepiston is between 16° and 18° and the defined angle between the secondlimb and the running surface of the piston is between 59° and 61°. Asealing ring designed in such a manner can also better withstand thehigh hydraulic pressure. As a result, the service life of the sealingring and therefore of the piston pump according to the invention islengthened and the downtimes of piston pump due to defective sealingrings are further minimized.

Advantageous embodiments of the invention are illustrated in thedrawings and are described below. In the drawings, the same referencenumbers denote components or elements which carry out identical oranalogous functions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows part of a piston pump having a filter and a guide ringbefore the filter and the guide ring are joined together, wherein agroove, in which a sealing ring according to the invention is insertedin a first embodiment, is formed between the two components.

FIG. 2 shows a sectional illustration of the piston pump from FIG. 1.

FIG. 3 shows a detail of the sectional illustration of the sealing ringaccording to the invention from FIG. 2, the sealing ring having asealing lip, the limbs of which enclose initial angles with the runningsurface of the piston.

FIG. 4 shows part of the piston pump after the filter and the guide ringare joined together, with the sealing ring according to the invention inthe installed state.

FIG. 5 shows a sectional illustration of the piston pump from FIG. 4.

FIG. 6 shows a detail of the sectional illustration of the sealing ringaccording to the invention from FIG. 5, the sealing ring having thesealing lip, the limbs of which enclose defined target angles with therunning surface of the piston, said target angles being achieved bydeformation of the sealing ring upon installation.

FIG. 7 shows a sectional illustration of a sealing ring according to theinvention in a second embodiment, said sealing ring forming twoencircling grooves on its inner circumferential surface, between whichgrooves the sealing lip is formed.

FIG. 8 shows a detail of the sectional illustration of the sealing ringaccording to the invention from FIG. 7.

EMBODIMENTS OF THE INVENTION

Various pump components, such as, for example, pump pistons which moveduring the pumping of a fluid which is to be conveyed or fixedcomponents sealing the moving pump pistons, such as, for example,sealing rings, are generally exposed to increased wear. The weargenerally relates to surface regions which are stressed by pressure orsurface pressure. For example the pump pistons become relatively greatlyworn due to oscillations, transverse forces and friction, wherein gapextrusion may regularly occur at the sealing ring and wear may regularlyoccur on the guide ring or on the eccentric shaft. For example, via abearing point between an eccentric and the pump piston, a rotationalmovement of a pump drive is converted into a lifting movement forgenerating pressure, as a result of which wear loads may occur in thebearing point. Therefore, pump pistons and sealing rings have to beprotected against increased wear in order to be able to maintain theirpumping and sealing function.

FIGS. 1 to 6 each show a cutout of a piston pump 12 which is used, forexample, as a feed pump or return pump of a hydraulic pumping system ofa vehicle. Since piston pumps of this type are known per se inconstruction and function, the drawing and description for the clearillustration of the invention are restricted to the relevant partaccording to the invention of the piston pump 12. The piston pump 12comprises a piston housing 14 which has a filter 50 a and a guide ring52 a and in which a piston 16 a is arranged, said piston beingaccommodated in an axially displaceable manner in a stepped piston bore54 a.

For the dynamic sealing of the piston 16 a guided in the piston housing14 a, a sealing ring 10 a, 10 b is inserted into an annular step of thepiston bore 54 a, wherein the sealing ring 10 a, 10 b is to be arrangedon an outer circumference of the piston 16 a, said outer circumferenceforming a running surface 18 a, 18 b. FIGS. 1 to 6 show a sealing ring10 a according to the invention in a first embodiment. FIGS. 7 and 8show a sealing ring 10 b according to the invention in a secondembodiment. The tubular filter 50 a which surrounds the piston 16 a andis inserted into the piston bore 54 a holds the sealing ring 10 a, 10 btogether with the guide ring 52 a axially in the piston bore 54 a by agroove 24 a, in which the sealing ring 10 a, 10 b is placed, beingformed between the two components 50 a, 52 a.

The sealing ring 10 a, 10 b comprises an annular basic body 20 a, 20 b,on the outer circumferential surface 22 a, 22 b of which at least oneencircling groove 24 a, 24 b is formed and on the inner circumferentialsurface 26 a, 26 b of which at least one encircling sealing lip 28 a, 28b is formed. The limbs 30 a, 30 b, 31 a, 31 b of the sealing lip 28 a,28 b each enclose a defined angle β_(1a), β_(2a) with the runningsurface 18 a, 18 b in the installed state of the sealing ring 10 a, 10b. In the present exemplary embodiments, a first limb 30 a, 30 b isacted upon axially with a higher pressure and a second limb 31 a, 31 bis acted upon axially with a lower pressure.

The sealing lip 28 a, 28 b is preferably formed centrally on the innercircumferential surface 26 a, 26 b and preferably has a radius R of atleast 0.1 mm, wherein larger radii, such as, for example, R=0.225 mm andgreater, would also be conceivable.

As has already been mentioned, the sealing ring 10 a, 10 b is arrangedin an annular step of the piston bore 54 a of the piston pump 12 a,which annular step is designed as a groove 24 a running in the pistonhousing 14 a and is acted upon axially on one side with a hydraulicpressure. The sealing ring 10 a, 10 b advantageously dynamically sealsthe piston 16 a which carries out a lifting movement in the insidediameter of the sealing ring 10 a, 10 b.

According to the invention, in order to increase the sealing effect ofthe sealing ring 10 a, 10 b, starting from initial angles α_(1a),α_(2a), α_(1b), α_(2b), the defined angles β_(1a), β_(2a) are achievedby deformation of the sealing ring 10 a, 10 b during installation. Forthis purpose, the sealing ring 10 a, 10 b undergoes a distortion γ_(a),γ_(b) about a center point of its profile during fitting. The distortionγ_(a), γ_(b) of the profile of the sealing ring 10 a, 10 b is preferablybetween 19° and 22°.

The initial angles α_(1a), α_(2a), α_(1b), α_(2b) of the limbs 30 a, 30b, 31 a, 31 b of the sealing lip 28 a, 28 b with respect to the runningsurface 18 a, 18 b are approximately 38.75°. In this case, a toleranceof at maximum 3 to 5° is preferably permitted. The contact surfaces 42a, 44 a, 46 a, 48 a of the sealing ring 10 a, 10 b are providedcentrally with an angle β_(1a), β_(2a). If the sealing ring 10 a, 10 bis compressed, provision is made for the ring 10 a, 10 b to be twistedper se about the angle β_(1a), β_(2a) cross section. By means of thetwisting, the sealing lip 28 a, 28 b is likewise twisted, as a result ofwhich the sealing lip limbs 30 a, 30 b, 31 a, 31 b take up an angle ofbetween 16° and 18°, ideally of 17.5° on the air side or low pressureside and an angle of between 59° and 61°, ideally of 60°, on the liquidside or high pressure side.

During fitting, the sealing ring 10 a undergoes a distortion γ_(a) ofits profile through preferably 21°. As a result, the angle α_(2a)changes from approximately 38° according to FIG. 3 on the fluid side orhigh pressure side between the second limb 31 a and the running surface18 a to approximately 60° according to FIG. 6. On the air side or lowpressure side, the angle α_(1a) drops from approximately 38° accordingto FIG. 3 between the first limb 30 a and the running surface 18 a atthe same time to approximately 18° according to FIG. 6. FIG. 3 shows thesealing ring 10 a together with the installation space before the filter50 a and the guide ring 52 a are fitted. In the installed stateaccording to FIGS. 5 and 6, contact surfaces 42 a, 44 a, 46 a, 48 a ofthe sealing ring 10 a each bear parallel to one another against thecorresponding surfaces 43 a, 45 a of the filter 50 a and thecorresponding surfaces 47 a, 49 a of the guide ring 52 a.

By means of the groove 24 a, 24 b in the outer cross section or on theouter circumferential surface 22 a, 22 b, the rigidity of the crosssection of the sealing ring 10 a, 10 b acts resiliently such that theinner sealing lip 28 a, 28 b is pressed onto the running surface 18 a,18 b as soon as the cross section is compressed.

FIGS. 7 and 8 show the second embodiment of the sealing ring 10 b whichhas two encircling grooves 32 b, 34 b on the inner circumferentialsurface 26 b of the sealing ring 10 b, said grooves forming two sealinglips 36 b, 38 b, between which the sealing lip 28 b is formed. Thesealing lip 28 b protrudes over the lips 36 b, 38 b in the radialdirection 40 b. The grooves 32 b, 34 b in the inner radius or on theinner circumferential surface 26 b are configured in such a manner thata radial or wedge-shaped shoulder 58 b can penetrate a gap h and therebyraises an inner edge 56 b until the latter runs parallel to the runningsurface 18 b. The shoulder 58 b is intended to have the height s and thelength f. The outer contour of the shoulder 58 b preferably has a radiuscorresponding to the radii of the inner grooves 32 b, 34 b. However saidinner grooves are intended to be short enough to avoid gap extrusion ofthe sealing lip 28 b and, in addition, have a rising profile whichpermits easy raising of the lip 38 b. It is also important for theheight h to be of a sufficient size as far as possible in order not tolie on the running surface 18 b in the deformed state and thereby to beat risk of gap extrusion on the non-raised side. The angle δ_(b) betweenthe inner edge 56 b and a side surface 60 b of the sealing ring 10 b ispreferably approx. 90°+/−10° in order to provide the sealing ring 10 bwith sufficient support on the shoulder 58 b.

An angle difference of the sealing lip limbs 30 b, 31 b of 60° minus17.5°=42.5° is produced and has to be compensated for per limb 30 b, 31b in each case by γ_(b)=42.5°/2=21.25°. This means that the sealing ring10 b undergoes a distortion γ_(b)=21.25° in order to form verticalcontact surfaces on both sides after the twisting of the sealing ring 10b. The initial angle α_(1b), α_(2b) is 60°−21.25°=38.75°=17.5°+21.25°.Depending on the dimensions of the sealing ring 10 b, h is predeterminedto be of a size such that, when the sealing ring 10 b is twisted, thelips 36 b, 38 b neither touch the running surface 18 b nor are at riskof gap extrusion.

In a refinement of the invention, further sealing lips and/or groovesand also sealing lips and/or grooves of different geometrical shapes mayalso be provided on the sealing ring 10 a, 10 b according to theinvention.

The described pump pistons and sealing rings are used, for example, inpump systems in modern vehicle technology, said pumping systems relatingby way of example to safety technology, such as ABS (anti-lock system),ESP (electronic stabilization program), EHB (electrohydraulic brake),TCS (traction control system) or ASR (anti-slip control). However, thesealing ring according to the invention can be used not only in thepreviously mentioned pumping systems but also in all systems in whichsealing rings stressed in a translatory and dynamically changing mannerare required.

1. A sealing ring for dynamically sealing a piston of a piston pump,comprising: an annular basic body having an outer circumferentialsurface with at least one encircling groove and having an innercircumferential surface with at least one encircling sealing lip,wherein the at least one encircling sealing lip has limbs, wherein, whenthe sealing ring is in an installed state, the limbs each enclose adefined angle with a running surface of an outer circumference of thepiston, and wherein the defined angles are formed, starting from initialangles, by deformation of the sealing ring during installation.
 2. Thesealing ring as claimed in claim 1, wherein the sealing ring isconfigured to be distorted about a center point of a profile duringfitting.
 3. The sealing ring as claimed in claim 1, wherein the profileof the sealing ring is distorted between 19° and 22°.
 4. The sealingring as claimed in claim 1, wherein: the inner circumferential surfacefurther includes two encircling grooves configured to form two lips, andthe sealing lip is formed between the two lips.
 5. The sealing ring asclaimed in claim 4, wherein the sealing lip protrudes over the lips in aradial direction.
 6. The sealing ring as claimed in claim 4, wherein thesealing lip has a radius between 0.1 and 0.4 mm.
 7. A piston pumpcomprising: a piston guided in one of a piston housing and a guide ring;and a sealing ring configured to dynamically seal the piston, thesealing ring including: an annular basic body having an outercircumferential surface with at least one encircling groove and havingan inner circumferential surface with at least one encircling sealinglip, wherein the at least one encircling sealing lip has limbs, whereinwhen the sealing ring is in an installed state, the limbs each enclose adefined angle with a running surface of an outer circumference of thepiston, and wherein the limbs have initial angles, and the definedangles are formed by deformation of the sealing ring duringinstallation.
 8. The piston pump as claimed in claim 7, wherein thesealing ring is arranged via at least three contact surfaces in a grooverunning between two components of the piston pump.
 9. The piston pump asclaimed in claim 7, wherein: the sealing ring has a first limb and asecond limb, the first limb is configured to be acted upon axially witha higher pressure, and the second limb is configured to be acted uponaxially with a lower pressure.
 10. The piston pump as claimed in claim7, wherein: a first defined angle between the first limb and a runningsurface of the piston is between 16° and 18°, and a second defined anglebetween the second limb and the running surface of the piston is between59° and 61°.